ACE716E - ACE Technology Co., LTD.

ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
Description
The ACE716E is a high efficiency step-up converter with an internally integrated 40V power MOSEFT.
It runs with an optimal 0.8MHz frequency that enables use of small external components while still
providing best efficiencies. It has an internal current limit as high as 1A, and it can drive up to 10 LEDs at
50mA output current. The incorporated 25-100KHz true PWM-Dimming feature by EN pin can be used to
digitally program the LED current. For maximum protection, the ACE716E has an internal OVP protection
at 38V to prevent the chip from damages when the LED string is not connected to the output.
ACE716E is available in a space-saving SOT23-6 package.
Features
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Up to 90% Efficiency (6 LEDs)
Drive up to 10 LEDs with 50mA
Drive up to 40 LEDs in total
38V OVP protection
True PWM Brightness Control
200mV Feedback Voltage
1A current limit
SOT23-6 Package
Application
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•
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Cellphone and Smartphone
MID or Tablet PC
TFT-bias for LCD screen
Power for OLED
LED torch
Satellite Set Top Box
Absolute Maximum Rating
Parameter
Value
SW Voltage
-0.3V~38V
All Other PIN Voltages
-0.3V~6.5V
SW to ground current
Internally limited
Operating Temperature Range
-40℃~85℃
Storage Temperature Range
-55℃~150℃
Thermal Resistance (Θjc)
SOT23-6
ΘJA
100
ΘJC
50
℃/W
Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability.
VER 1.2
1
ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
Packaging Type
SOT-23-6
Ordering information
ACE716E XX + H
Halogen - free
Pb - free
GM: SOT-23-6
PIN
NAME
DESCRIPTION
1
SW
Inductor Connection. Connect an inductor Between SW and IN.
2
GND
Ground Pin
3
FB
Feedback Input for Current. Connect an external resistor FB to GND to set IOUT
4
EN
Control pin for the IC. It is default low. It is a multi-functional pin for enable control,
PWM dimming
5
NC
Not connected, leave this PIN floating
6
IN
Input Supply pin. Bypass with a 4.7μF or larger ceramic capacitor to GND
VER 1.1
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ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
BLOCK DIAGRAM
Electrical Characteristics
(VIN =3.6V, unless otherwise specified.Typical values are at TA=25℃)
Parameter
Conditions
Input Voltage Range
FB Feedback Voltage
Min
Typ
2.7
VIN=VCTRL=3.6V
194
200
FB Input Current
Max
Unit
6
V
206
mV
2
uA
1.8
mA
5
mA
uA
Quiescent Current at IN
Switching at lout=0
1.0
Quiescent Current at IN
Shutdown Supply Current at IN
No Switching
0.2
VEN=GND
0
Switching Frequency
VIN<4.3V
0.8
MHz
93
%
Maximum Duty Cycle
90
NMOS Switch On Resistance
lSW=100mA
0.44
Ω
NMOS Switch Current Limit
VIN*3.6V, 10LEDS
1.0
A
SW Leakage Current
VSW=0 or 20V, VEN=GND
EN Inupt Current
0.1
EN Input Low Voltage
EN Input High Voltage
1.2
PWN dimming frequency
25
Thermal Shutdown
Rising, Hysteresis=10℃
10
uA
1
uA
0.6
V
V
100
165
KHz
℃
VER 1.1
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ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
Typical Application
USB Power Application Circuit
VOUT = 0.2x(1+R1/R2)
Note: The Pin6, Vin Pin of ACE716E
is connected to 5V, not the battery input.
Circuit lefthand is only for output than 5.5V!
Please connect Pin6 to input if output is to
Be larger than 5.5V.
VER 1.1
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ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
TFT Bias Application Circuit
Typical Application Circuit
(Typical values are at TA=25℃ unless otherwise specified)
VER 1.1
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ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
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ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
FUNCTIONAL DECRIPTIONS
The ACE716E is a high efficiency boost LED driver with a small package size. The device is ideal for
driving 2-25LEDs for backlight application in smartphone and 7-inch tablet PC. The device integrates a
38V/1A switch FET and operates in pulse width modulation (PWM) with a 0.8MHz fixed switching
frequency. For operation details, please check the block diagram in the “Block Diagram” chapter. The duty
cycle of the converter is set by the error amplifier output and the current signal applied to the PWM
control comparator. The feedback loop regulates the FB pin to a low reference voltage (200mV typical),
reducing the power dissipation in the current sense resistor.
Output Open Circuit Protection
Output open circuit protection circuitry prevents IC damage as the result of output open circuit (e.g. LED
string absence). The ACE716E monitors the voltage at the SW pin and FB pin during each switching
cycle. The circuitry turns off the switch FET and shuts down the IC when both of the following conditions
persist for 8 switching clock cycles: (1) the SW voltage exceeds the VOVP threshold, which is 38V and (2)
the FB voltage is less than half of regulation voltage. As a result, the output voltage falls to the level of the
input supply. The device remains in shutdown mode until it is enabled by toggling the EN pin logic. The
output voltage plus the 200mV reference voltage cannot exceed the minimum OVP threshold or OUTPUT
VOLTAGE + 200 mV ≤ VOVP(MIN).
Shutdown
The ACE716E enters shutdown mode when the EN voltage is logic low for more than 3ms. During
shutdown, the input supply current for the device is less than 1μA (max). Although the internal FET does
not switch in shutdown, there is still a DC current path between the input and the output through the
inductor and Schottky diode.
For LED driving application, the minimum forward voltage of the LED array must exceed the maximum
input voltage to ensure that the LEDs remain off in shutdown. However, in the typical application with two
or more LEDs, the forward voltage is large enough to reverse bias the Schottky and keep leakage current
low.
LED Driving Current Setting
The FB voltage is regulated by a low 0.2V reference voltage. The LED current is set externally using a
current-sense resistor in series with the LED string. The value of the RSET is calculated using Equation
1.2:
ILED =0.2/RSET
(1.2)
Where
ILED = output current of LEDs, RSET = current sense resistor
The output current tolerance depends on the FB accuracy and the current sensor resistor accuracy.
PWM Dimming Control or Output Voltage Programming
When the CTRL pin is constantly high, the FB voltage is regulated to 200mV typically. However, the EN
pin allows a PWM signal to reduce this regulation voltage; therefore, it achieves LED brightness dimming
or output voltage programming (only to make output voltage lower). The relationship between the duty
cycle and FB voltage is given by Equation 2.
VER 1.1
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ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
VFB =Duty*200 mV
(2)
Where
Duty = duty cycle of the PWM signal, 200 mV = internal reference voltage
This PWM dimming eliminates the audible noise which often occurs when the output current is pulsed in
replica of the frequency and duty cycle of PWM control. Unlike other scheme which filters the PWM signal
for analog dimming, ACE716E regulation voltage is independent of the PWM logic voltage level which
often has large variations For optimum performance, use the PWM dimming frequency in the range of
25kHz to 100kHz.
APPLICATION INFORMATION
Inductor Selection
Using an inductor with a smaller inductance value forces discontinuous PWM when the inductor current
ramps down to zero before the end of each switching cycle. This reduces the boost converter’s maximum
output current, causes large input voltage ripple and reduces efficiency. Large inductance value provides
much more output current and higher conversion efficiency. For these reasons, a 15μH to 22μH inductor
value range is recommended. A 15μH inductor optimized the efficiency for most application while
maintaining low inductor peak to peak ripple. Below table lists the recommended inductor for the
ACE716E.
Recommended Inductors for ACE716E
L(uH)
Saturation Current (mA)
4.7- 15
>1500
Vendor
Sunlord
Schottky Diode Selection
A high-speed rectifying Schottky with low parasitic capacitance is recommended for ACE716E for
maximum efficiency due to its high switching frequency. The diode average and peak current rating
must be larger than the average output current and peak inductor current to ensure reliability. In addition,
the diode’s reverse breakdown voltage must exceed the open LED protection voltage.
Input and Output Capacitor Selection
The output capacitor is mainly selected to meet the requirements for the output ripple and loop stability.
The output requires a capacitor in the range of 2.2μF to 10μF.
VER 1.1
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ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
Packing Information
SOT-23-6
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ACE716E
Max 38V, Variable Frequency Step-up DC/DC Converter
Notes
ACE does not assume any responsibility for use as critical components in life support devices or systems
without the express written approval of the president and general counsel of ACE Electronics Co., LTD.
As sued herein:
1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and shoes failure to perform when properly used in
accordance with instructions for use provided in the labeling, can be reasonably expected to result in
a significant injury to the user.
2. A critical component is any component of a life support device or system whose failure to perform can
be reasonably expected to cause the failure of the life support device or system, or to affect its safety
or effectiveness.
ACE Technology Co., LTD.
http://www.ace-ele.com/
VER 1.1
10